1. Field of the Invention
The present invention relates to electrophotographic image forming apparatuses, for example, laser beam printers, copying machines, facsimiles, or multi-function printers being the combination thereof.
Furthermore, the present invention, in such image forming apparatuses, relates to remaining amount detecting methods of a developer contained in a developer containing portion of a developing device for developing an electrostatic latent image, which is formed on an electrophotographic photosensitive member.
2. Description of the Related Art
FIG. 21 illustrates one example of electrophotographic image forming apparatuses from which a process cartridge is constructed to be removable.
In this example, a process cartridge 13 includes a drum-shaped electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1, being an image bearing member rotating in a direction indicated by the arrow A in FIG. 21. With a charger 2 uniformly charging the photosensitive drum 1 and an exposure device 6 irradiating an optical image on the photosensitive drum 1, an electrostatic latent image is formed on the photosensitive drum 1. The electrostatic latent image on the photosensitive drum 1 is developed into a visible image by a developing device 3, which contains a developer (hereinafter referred to as “toner”) T. Further, the visible image that is a toner image is transferred onto a recording sheet P by a transfer device 4. The toner image having been transferred onto the recording sheet P is fixed by a fixing device 7.
On the other hand, toner remaining on the photosensitive drum 1 after transfer is removed by a cleaning device 5.
The above-mentioned photosensitive drum 1, charger 2, developing device 3, and cleaning device 5 are integrally made into a process cartridge 13.
FIG. 22 is a view illustrating one example of a conventional developing device 3 of the same construction as the developing device 3 of the above-mentioned process cartridge 13.
The developing device 3 is provided with a developing container 3a as a developer containing portion. In the developing container 3a, there are provided a developing sleeve 8 as a developer carrying member carrying and conveying the contained toner T, a developing blade 11 regulating the layer of toner T carried on the developing sleeve 8 into a uniform thickness, and an agitating member 10 agitating toner in the developing container 3a. 
Furthermore, there is disposed in the developing container 3a an antenna member 14 as a toner remaining amount detecting member forming a developer (toner) remaining amount detecting unit for detecting the remaining amount of toner in the developing container 3a. 
As a toner remaining amount detecting unit, as illustrated in FIG. 22, one that detects the change in capacitance accompanied with the change of remaining amount of toner in the developing container 3a with an antenna member 14 disposed in parallel with the developing sleeve 8, to estimate the remaining amount of toner, is known (see Japanese Patent Application Laid-Open No. H09-190067).
In addition, a toner remaining amount detecting unit may be one that estimates the remaining amount of toner and detects troubles of the agitating member 10 by utilizing the band of fluctuation in capacitance fluctuating in association with rotation of the agitating member 10 (see Japanese Patent Application Laid-Open No. 2001-242690).
However, there have been the following problems in the above-mentioned conventional examples.
That is, recently owing to downsizing of a developing device 3, a difference between the electrical capacitance (hereinafter simply reffered to as either “capacitance” or “capacitances”) in the case of sufficient remaining amount of toner and the capacitance in the case of small remaining amount of toner becomes small. Therefore, in a toner remaining amount detecting unit disclosed in Japanese Patent Application Laid-Open No. H09-190067, the amount of change in capacitance necessary for making detection when the remaining amount of toner becomes small, that is, for detecting that the amount of toner becomes low (hereinafter referred to as toner LOW) becomes smaller.
Furthermore, in a toner remaining amount detecting unit disclosed in Japanese Patent Application Laid-Open No. 2001-242690, toner remaining amount detection is made based on the band of fluctuation in capacitance in association with rotation of an agitating member. In this case, toner remaining amount detection can be made even if there is just a small amount of change in capacitance when toner sufficiently remains and when the amount of toner becomes low. However, the band of fluctuation in capacitance in association with rotation of an agitating member differs depending on the position of an antenna member, or use environment even if remaining amounts of toner in a developing container are the same.
Accordingly, by the method of detecting that the band of fluctuation has reached a reference value having been preliminarily set as in Japanese Patent Application Laid-Open No. 2001-242690, errors are likely to occur between the remaining amount of toner having been detected and an actual remaining amount of toner.